Abstract
The first part of the physics programme of the integrated FCC (Future Circular Colliders) proposal includes measurements of Standard Model processes in e+e− collisions (FCC-ee) with an unprecedented precision. In particular, the potential precision of the Z lineshape determination calls for a very precise measurement of the absolute luminosity, at the level of 10−4, and the precision on the relative luminosity between energy scan points around the Z pole should be an order of magnitude better. The luminosity is principally determined from the rate of low-angle Bhabha interactions, e+e−→ e+e−, where the final state electrons and positrons are detected in dedicated calorimeters covering small angles from the outgoing beam directions. Electromagnetic effects caused by the very large charge density of the beam bunches affect the effective acceptance of these luminometers in a nontrivial way. If not corrected for, these effects would lead, at the Z pole, to a systematic bias of the measured luminosity that is more than one order of magnitude larger than the desired precision. In this note, these effects are studied in detail, and methods to measure and correct for them are proposed.
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References
M. Benedikt et al., Future Circular Collider — European Strategy Update Documents: The FCC integrated programme (FCC-int), CERN-ACC-2019-0007, (2019).
FCC collaboration, FCC-ee: The Lepton Collider, Eur. Phys. J. Spec. Top.228 (2019) 261 [INSPIRE].
OPAL collaboration, Precision luminosity for Z0 line shape measurements with a silicon tungsten calorimeter, Eur. Phys. J.C 14 (2000) 373 [hep-ex/9910066] [INSPIRE].
B.F.L. Ward, S. Jadach, W. Placzek, M. Skrzypek and S.A. Yost, Path to the 0.01% Theoretical Luminosity Precision Requirement for the FCC-ee (and ILC), in International Workshop on Future Linear Colliders (LCWS 2018) Arlington, Texas, U.S.A., October 22–26, 2018, 2019, arXiv:1902.05912 [INSPIRE].
C. Rimbault, P. Bambade, K. Monig and D. Schulte, Impact of beam-beam effects on precision luminosity measurements at the ILC, 2007 JINST2 P09001 [INSPIRE].
D. Schulte, Beam-Beam Simulations with GUINEA-PIG, CERN-PS-99-014-LP (1999).
M. Boscolo et al., Machine detector interface for the e+e−future circular collider, in Proceedings, 62nd ICFA Advanced Beam Dynamics Workshop on High Luminosity Circular e+e−Colliders (eeFACT2018): Hong Kong, China, September 24–27, 2018, arXiv:1905.03528 [INSPIRE].
J.F. Crawford, E.B. Hughes, L.H. O’Neill and R.E. Rand, A Precision Luminosity Monitor for Use at electron-Positron Storage Rings, Nucl. Instrum. Meth.127 (1975) 173 [INSPIRE].
G. Barbiellini, B. Borgia, M. Conversi and R. Santonico, A monitoring system to measure the absolute luminosity of a machine operating with e+e−colliding beams, Atti Accad. Naz. Lincei144 (1968) 233.
S. Jadach, W. Placzek and B.F.L. Ward, BHWIDE 1.00: O(α) YFS exponentiated Monte Carlo for Bhabha scattering at wide angles for LEP-1/SLC and LEP-2, Phys. Lett.B 390 (1997) 298 [hep-ph/9608412] [INSPIRE].
M. Bassetti and G.A. Erskine, Closed Expression for the Electrical Field of a Two-dimensional Gaussian Charge, CERN-ISR-TH/80-06, (1980).
E. Keil, Beam-beam dynamics, proceedings of the 5th Course of the CERN Accelerator School, Rhodes, Greece, September 20 – October 1, 1993, Vol. 1, 2, Conf. Proc.C9309206 (1993) 539 [CERN-SL-94-78-AP] [INSPIRE].
T. Hahn, CUBA: A library for multidimensional numerical integration, Comput. Phys. Commun.168 (2005) 78 [hep-ph/0404043] [INSPIRE].
T.M. Karbach, G. Raven and M. Schiller, Decay time integrals in neutral meson mixing and their efficient evaluation, arXiv:1407.0748 [INSPIRE].
A. Blondel et al., Polarization and Centre-of-mass Energy Calibration at FCC-ee, arXiv:1909.12245 [INSPIRE].
GEANT4 collaboration, GEANT4: A simulation toolkit, Nucl. Instrum. Meth.A 506 (2003) 250 [INSPIRE].
I. Sadeh, Luminosity Measurement at the International Linear Collider, Ph.D. thesis, Tel Aviv University, 2010, [arXiv:1010.5992] [INSPIRE].
F. Zimmermann, Collider Beam Physics, Rev. Accel. Sci. Tech.7 (2014) 177 [INSPIRE].
G. Voutsinas, E. Perez, M. Dam and P. Janot, Beam-beam effects on the luminosity measurement at LEP and the number of light neutrino species, to be published in Phys. Lett.B [arXiv:1908.01704] [INSPIRE].
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Voutsinas, G., Perez, E., Dam, M. et al. Beam-beam effects on the luminosity measurement at FCC-ee. J. High Energ. Phys. 2019, 225 (2019). https://doi.org/10.1007/JHEP10(2019)225
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DOI: https://doi.org/10.1007/JHEP10(2019)225